Low-complexity QoS-aware frequency provisioning in downlink multi-user multicarrier systems

摘要

This paper studies quality-of-service (QoS)-aware frequency provisioning schemes for a downlink multi-user multi-carrier system in a frequency-selective fading environment with diverse user-QoS requirements in terms of target delay and effective capacity (EC). Since a jointly optimal power and sub-carrier allocation requires an exponential-time exhaustive search, we explore an alternative simpler approach with two steps: (i) frequency provisioning to allocate the available subcarriers to the demanding users, followed by (ii) power allocation for the set of subcarriers assigned to each user. The single-user EC-based power allocation can be directly applied to step (ii). Furthermore, its results can also be used to develop a low-complexity knowledge-based frequency provisioning algorithm for step (i). The proposed iterative frequency provisioning algorithm starts with an initial rate-based guess and analyzes the incremental cost of power with respect to each user's QoS requirement to modify the allocated numbers of subcarriers that can further reduce the power consumption, if possible, in each subsequent iteration. Illustrative results show that the initial rate-based guess can be very effective in many situations, whereas, when the demanding users have similar required ECs but widespread delay requirements, the initial rate-based guess can be far from the optimum solution and therefore, more iterations are needed.